What if motors were operated with water?

Myths about the hydrogen car: the truth about the fuel cell

  1. Fuel cell cars are dangerous
  2. Storage is complicated
  3. Hydrogen cars need a lot of energy
  4. Hydrogen production costs energy
  5. The bad carbon footprint
  6. Fuel cells need a lot of platinum
  7. Water vapor is a climate gas
  8. Hydrogen filling stations are expensive
  9. Fuel cell cars remain rare

1. Fuel cell cars are dangerous

This rumor persists, probably because of the demonstration of the oxyhydrogen reaction in chemistry class. What is correct: Hydrogen (H2) burns when oxygen is nearby and forms an ignitable mixture with oxygen in a wide range (H2 content from 4 to 75 percent). An explosive mixture (oxyhydrogen) with oxygen only forms hydrogen with a proportion of 18 percent or more. But that doesn't happen so easily with hydrogen - because hydrogen is a good 14 times lighter than air, it evaporates quickly. It is more problematic when hydrogen is trapped in cavities that are closed at the top. However, they would have to be closed very tightly because hydrogen penetrates through the smallest of cracks.

For example, if it escapes from the pressure tank of a car, it will quickly get on and off before it can mix with the oxygen in the ambient air. Researchers working with Michael Swain from the University of Miami demonstrated this with a test back in 2003. They set two cars on fire, one with a petrol tank and the other with a pressurized hydrogen tank. The researchers had previously drilled a small hole in each of the fuel lines. What happened? As expected, both vehicles caught fire. There were differences, however, in the course of the process: the petrol engine was ablaze after 60 seconds, the hydrogen car remained largely undamaged because the hydrogen burned very quickly in a huge jet of flame that shot up far above the vehicle. But as a result it quickly went out again. The car with a petrol tank, on the other hand, burned out completely, as happens again and again in real traffic.

Conclusion: Hydrogen is flammable in combination with oxygen and above a certain ratio a mixture is explosive. But hydrogen is extremely volatile because it is so light. In practice, it is arguably less dangerous than other car fuels. Fuel cell cars do not pose a particular risk of explosion. The risk of fire is greater in cars with gasoline or diesel tanks.

Hydrogen can only be stored in tanks with losses

In the BMW Hydrogen 7, which burned hydrogen in a conventional reciprocating engine, the hydrogen was stored in a very cold (-250 degrees) liquefied tank in a highly thermally insulated tank. Despite the insulation, the hydrogen in the tank becomes warmer and evaporates over time. The hydrogen gas produced must be able to escape from the tank so that the pressure does not become too high. If it cannot be used, there will be significant losses. The half-full liquid hydrogen tank of the Hydrogen 7 emptied itself in 9 days if not used. That would not be a problem for the environment, but it would be for the user.

The current fuel cell cars carry the hydrogen in gaseous form in 700 bar pressure tanks. With the tanks one gained experience not least with natural gas cars (pressure up to 200 bar). They have multilayer walls made of different materials so that even the small hydrogen atoms cannot diffuse through the tank walls. The losses due to escaping hydrogen are therefore now marginal. On the other hand, losses continue to occur when compressing. Most sources put it at a good 12 percent.

The high pressure makes the tanks complex. The tank system currently weighs around 125 kilograms and holds about 4.4 kilograms in the Mercedes GLC F-Cell. The consumption per 100 kilometers is around one kilogram, so that the GLC should travel a good 400 kilometers with the energy from the fuel cell. In a Tesla Model S with a similar range, the battery weighs around 650 kilograms.

Conclusion: Natural gas cars have advanced the technology for tanks in recent years; there are no longer any significant losses due to leakage or diffusion.

Hydrogen cars need a lot of energy

According to Prof. Dr. Christian Mohrdieck, Managing Director of Mercedes-Benz Fuel Cell GmbH and responsible for fuel cell development in the Daimler Group, an efficiency of 83 percent, the overall vehicle comes to a good 50 percent. Electric cars achieve 90 percent efficiency. Losses occur here primarily with fast charging - then the efficiency can drop to 75 percent.

But: According to Mohrdieck, the fuel cell is already about twice as efficient as an internal combustion engine. Depending on the company, it is up to 65 percent. The overall energy balance is correspondingly significantly better. Important: The fuel cell is an energy converter - it converts hydrogen into electricity. Therefore, such a system can never be as efficient as a battery, which is an energy store. However, this weakness is also a strength: The waste heat from the fuel cell system can also be used to heat the vehicles.

If you look at the entire chain from hydrogen production to conversion into electrical or kinetic energy, according to Mohrdieck, you actually come to an efficiency of only 29 to 32 percent. This means that the fuel cell car is only slightly better than gasoline (22 percent) or diesel (25 percent). But even the electric car is only marginally better than the fuel cell car from a well-to-wheel perspective (including power generation). And even if the hydrogen is obtained from natural gas, the efficiency of the fuel cell car is about 25% better than that of the gasoline-powered car.

Battery vehicles are more efficient

Maximilian Fichtner, Professor of Solid State Chemistry at the University of Ulm, calculated in November 2019 in Wirtschaftswoche, however, that traffic in Germany has an annual energy requirement of around 770 terawatt hours. "With a fleet with pure hydrogen drives such as the fuel cell, you would need up to 1000 terawatt hours because of the poorer overall efficiency. The electric car is several times more efficient: A purely electric fleet with battery vehicles would get by with around 200 terawatt hours of energy per year".

The big advantage of hydrogen: As a portable storage device for large amounts of energy it is unbeatable - as a stationary energy storage device it is even more superior to batteries: more versatile, more flexible, cheaper. Maximilian Fichtner is therefore not fundamentally against the use of hydrogen, but does not see it in the car, "but in the stationary area, as a storage in the power supply for volatile renewables, and partly also in heavy goods traffic or on ships, and of course in industry" .

Conclusion: There is no efficiency disadvantage of hydrogen cars compared to cars with internal combustion engines. On the contrary: even with the production of hydrogen from fossil fuels, the efficiency is better than with the combustion engine. Compared to the electric car, however, the fuel cell car well to wheel is worse because generating the hydrogen with electricity and converting it back into electricity nibble twice on the efficiency. Added to this is the energy required for storage and refueling. Hydrogen is better suited to this as a transportable energy storage device. If it is possible to generate enough green electricity, which, according to Prof. Maximilian Fichtner, is not so clear, the efficiency discussion is basically academic. Because the goal of alternative drives is to reduce CO2 emissions. And it looks good for the hydrogen car. But that's a story of its own.

Hydrogen does not exist in nature, its production costs energy

Hydrogen, as Wikipedia knows, "is the most abundant chemical element in the universe, but not in the earth's crust". Indeed, the exploitation of molecular hydrogen resources on earth is practically impossible. On the other hand, hydrogen is comparatively easy to obtain, in principle in any quantity, since hydrogen is contained in water. In principle, it can also be generated from fossil fuels such as natural gas. On the other hand, generation by electrolysis is potentially "green" - if the electricity required for this is generated in a CO2-neutral manner. To put it simply, electrolysis works by energizing a water basin. Then hydrogen rises at the cathode and oxygen at the anode. The two combined generate electricity (and water) again via fuel cells. In principle a wonderful cycle - if the electricity is generated CO2-neutrally. Because electrolysis has an efficiency of 60 to 70 percent, but the hydrogen is then converted back into electricity. The double conversion has the negative effect on the efficiency described above.

However, assuming CO2-neutral electricity generation, which is already on the agenda, efficiency no longer plays the decisive role. Then the storage and transport capacity comes to the fore, because especially with alternative energy generation large peaks and slacks must be expected, which is why experts expect that 200 to 300 terawatt hours must be stored when generating electricity from alternative sources. Often the energy is created where it is not needed. Hydrogen generation as an intermediate storage is a perfect fit for this, while storing electricity using batteries is far too expensive.

In addition, hydrogen could also play an important role in reducing CO2 in the production of steel. Coke (made from coal) is currently used as a fuel and reducing agent in blast furnaces. The steelworks in Germany alone emit around 50 million tons of CO2 per year (car traffic 2017: 115 million tons). If you use hydrogen instead of coke, the steel production itself does not produce any CO2. However, the steel then has to be heated with more external energy and the hydrogen generated. If it is generated from regenerative sources, like heat energy, the potential for CO2 savings is close to 100 percent - the industry also wants to become CO2-neutral by 2050 in accordance with the Paris Climate Agreement.

What does this have to do with hydrogen cars? First of all, they are largely made of steel and, secondly, a whole industry would need a lot more hydrogen than traffic should ever need, in other words: A lot of hydrogen would probably be produced, so that the supply of cars would not be a problem. The amount of hydrogen currently produced in Germany was enough for around 750,000 cars.

Conclusion: Yes, hydrogen is practically not stored in underground fields like oil for example. But its generation with the help of regeneratively generated electrical energy and its storage are proven and technologically simple. The fuel cell car should not fail because of this.

survey

Should we all run on hydrogen in the future?
Definitely! The fuel cell combines potentially CO2-free driving with a range for refueling.
No! Fuel cell cars are no more CO2-neutral than e-cars and there will never be enough affordable hydrogen.

The CO2 balance of the hydrogen car is bad

That is a fallacy. Battery-powered cars are hard to beat when it comes to tank-to-wheel efficiency (i.e. from charging with electricity to driving). But even with hydrogen obtained from natural gas, the hydrogen car is around 25 percent better than cars with a combustion engine when viewed well-to-wheel. And with the current electricity mix, the CO2 balance of the fuel cell car is slightly better than that of the electric car over its entire service life.

And as far as production is concerned, there is nothing to prevent fuel cell vehicles from developing in the same way as electric cars. In production, they still cause 80 percent higher CO2 emissions than a combustion engine. However, when driving with a conventional electricity mix, you save around 65 percent CO2 compared to this. As a result, their total CO2 emissions over the entire life cycle are at least 40 percent lower with the same mileage.

If the battery-powered vehicle can only be operated with renewable electricity, its CO2 emissions will decrease by 70 percent over the life cycle compared to the combustion engine. The fuel cell drive comes to very similar figures, which produces fewer emissions than battery-powered vehicles, but slightly more emissions when driving, and where the provision of hydrogen has a major influence on the overall effect.

Above all, the lead of e-cars in terms of CO2 balance will continue to grow in the future. Because, as it is said at Mercedes, "the optimization of battery technology and production offers great potential for further savings. Today's batteries already produce around 25 percent less CO2 emissions than traction batteries of the first generation. For the next generation Experts expect savings of the same order of magnitude: The production of future batteries will therefore only cause half the CO2 emissions of the first generation, and a third less than those of today.

Conclusion: Overall, the fuel cell car is at least as low in CO2 as the purely battery-electric car, despite its own (comparatively smaller) battery. But with hydrogen you can refuel within minutes without having to carry large and therefore heavy batteries. The latter also qualifies the fuel cell for commercial vehicles.

Fuel cells need a lot of scarce platinum

As one likes to talk about cobalt or lithium in the case of electric cars, which would make mass production impossible, there are similar objections to the fuel cell. Because to make them you need platinum, an expensive precious metal.

On the other hand, we have been using platinum in the catalytic converters of gasoline vehicles since the 1980s. You don't hear any discussions about it, however. Do you need so much more platinum for a fuel cell than for a catalytic converter in an internal combustion engine? In fact, the Mercedes B-Class F-Cell still had a fuel cell with a high platinum content. Even today, platinum is still used as a catalyst in the stack. With the new GLC F-CELL, Mercedes was able to reduce the amount of platinum compared to the hydrogen B-Class by 90 percent and in the next step, Prof. Mohrdieck promises, "will be only a little more than the catalyst of a comparable gasoline engine (8-10g) ".

However, according to Mohrdieck, a lot of research is still needed to replace platinum in fuel cells. But the recycling rate for platinum in gasoline-powered cats is already 98 percent. Similar values ​​are also conceivable for fuel cells, according to Mohrdieck.

Conclusion: The platinum requirement for mass-produced fuel cell cars is no higher than that for modern gasoline-powered vehicles.

Fuel cell cars produce the greenhouse gas water vapor

Water vapor generally leads to warming in the atmosphere and is therefore also referred to as a climate gas. But when operating a fuel cell car, surprisingly, hardly any more water is emitted than a combustion engine, because gasoline consists of hydrocarbons. When it is burned, water vapor is also released. However, the water vapor in fuel cell cars has much lower temperatures and condenses earlier. That is why some of the water that occurs during operation is collected and reused to humidify the fuel cell. Black ice risk from fuel cell cars is therefore also not to be expected.

In aircraft with fuel cell propulsion, water recovery would be worthwhile: You could save around 90 percent of the water for the toilets - an exciting option for mobile homes too.

Conclusion: The fact that water is produced when fuel cell cars are operated is neither a problem for the environment nor for traffic.

Nobody can afford fuel filling stations

Most experts currently estimate the cost of building a hydrogen filling station to be around 1,000,000 euros. At the same time, around 1,000 petrol stations are estimated for a nationwide network in Germany. The infrastructure for fuel cell cars would come to around one billion euros. Sounds like a lot, but it isn't. For comparison: the diesel scandal has cost the Volkswagen Group around 28 billion euros to date.

Like the cars, hydrogen filling stations could also become considerably cheaper due to economies of scale in a type of mass production (approx. 400,000 euros instead of approx. 1,000,000 euros now).

Conclusion: The mass distribution of fuel cell cars should not fail because of the infrastructure. At most, the establishment of more hydrogen filling stations will fail due to the currently not yet massive spread of fuel cell cars - a classic chicken-and-egg problem.

Fuel cell cars remain a niche product

In view of the undeniable advantages, especially in times of climate change, the question arises: Why is the hydrogen car not (yet) coming? The massive spread of fuel cell cars is currently still failing because the production of the cars is too expensive and the infrastructure, which is also expensive. According to Professor Mohrdieck, both are challenges that can be solved by scaling. With six-digit numbers or more, a fuel cell vehicle can be produced at a cost similar to that of a battery-electric car, Mohrdieck is certain. One step towards a discount is the production of the fuel cell from roll to roll of the MEA (Membrane Electrode Assembly), i.e. the core component of the cell. Currently it is still being developed individually.

Overall, Mohrdieck estimates the future of the fuel cell car as follows: "The fuel cell drive is particularly interesting for customers who need a high daily range and have access to hydrogen filling stations. For vehicles in urban areas, however, a purely battery-electric drive is a very good solution today . The Mercedes GLC F-CELL (as a hybrid of both types of drive) is an important step for us, even if we do not yet represent large vehicle volumes. We are very excited about the feedback from our customers. Battery and fuel cell form a symbiosis. The two Technologies complement each other very well: The performance and dynamics of the battery support the long-range and quickly refuelable fuel cell, which is ideally operating in the partial load range ".

"A combination of scalable battery or fuel cell modules would be conceivable in the future - depending on the mobility scenario and vehicle type. We are only at the beginning. I think that by the middle of the next decade - but certainly after 2025 - the relevance of fuel cells in general and for the transport sector will become significant Even moderate volumes will help to create standards that are particularly essential for reducing costs ".

In conclusion, Mohrdieck says: "For a technology to make a breakthrough, it must be attractive for both sides - the customer and the manufacturer".

Conclusion: The main obstacles to the mass spread of fuel cell cars are their expensive production and lack of infrastructure. Both can be discounted through mass production, of all things. Fuel cell cars are not in principle, but only currently expensive and do not have to remain a niche product.